Rename EventInformation class to AtlasG4EventUserInfo
The EventInformation class inherits from the G4VUserEventInformation class.
It is used to pass around additional information about the truth particle
currently being processed.
However, the name is very similar to the (xAOD::)EventInfo object used
elsewhere in Athena. In order to avoid this clash this merge request renames the
EventInformation class to AtlasG4EventUserInfo.
This merge request is a bit of preliminary tidying to make migrating the
simulation step to use xAOD::EventInfo easier in the future.
FYI @mbandier, @mmuskinj, @zmarshal, @mduehrss